Professor at Universitt̃ Stuttgart, 1921-1937; visits the U.S. in 1936 (University of Michigan Summer School). Political climate in Germany and Ewald's dismissal from Stuttgart; works on foundations of crystal optics while living in mother's house. Leaves Germany on a research fellowship from University of Cambridge, 1937-1939; professorship at Belfast University, 1939-1949. Relationship with Hans Bethe; comments on his children. Discussion of Ewald's scientific contributions, in particular, the dynamics theory; comments on Max von Laue. Worked as x-ray technician during World War I; stationed in Russia for three years (Otto Blumenthal). On the rewriting of the dynamics theory and problems still to be solved.